Imagick::getImageCompression

Example use:

$im = new Imagick("mypicture.jpg");
$ctype = $im->getImageCompression();
if($ctype == Imagick::COMPRESSION_ZIP) echo "PNG file!";
if($ctype == Imagick::COMPRESSION_JPEG) echo "JPG file!";
if($ctype == Imagick::COMPRESSION_LZW) echo "GIF file!";

All options:
COMPRESSION_UNDEFINED
COMPRESSION_NO
COMPRESSION_BZIP
COMPRESSION_FAX
COMPRESSION_GROUP4
COMPRESSION_JPEG
COMPRESSION_JPEG2000
COMPRESSION_LOSSLESSJPEG
COMPRESSION_LZW
COMPRESSION_RLE
COMPRESSION_ZIP
COMPRESSION_DXT1
COMPRESSION_DXT3
COMPRESSION_DXT5
COMPRESSION_ZIPS
COMPRESSION_PIZ
COMPRESSION_PXR24
COMPRESSION_B44
COMPRESSION_B44A
COMPRESSION_LZMA
COMPRESSION_JBIG1
COMPRESSION_JBIG2

The numbers for which those constants stand differ by version. So always use the constants.

This function is added in version 3.3.0 and above

This function is undefined. You must use getImageCompressionQuality() instead.